Biology subjects

Dion, S.

Publications and source records attributed to Dion, S..

7 recordsLinked to original sources

bioRxiv2026

Repurposing Niclosamide Ethanolamine for Alveolar Echinococcosis Reveals a Disconnect Between In Vitro Efficacy and In Vivo Outcome

BackgroundEchinococcosis is a zoonotic disease caused by cestodes of the genus Echinococcus. Alveolar echinococcosis (AE), caused by E. multilocularis, primarily affects the liver and shows infiltrative, tumor-like growth of the metacestode stage. If untreated, AE is lethal. AE remains a neglected disease with current treatments based on albendazole or mebendazole that are parasitostatic, and not curative, underscoring the need for more effective therapies. Niclosamide is a chlorinated salicylanilide derivative with proven activities against intestinal helminths but is inactive against tissue-dwelling helminths due to poor absorption and limited bioavailability. In this study, we repurposed niclosamide ethanolamine (NEN), a formulation with improved systemic exposure, for the treatment of E. multilocularis infection in vitro and in vivo. Methodology/Principal FindingsWe assessed the in vitro efficacy of niclosamide and NEN against E. multilocularis metacestode vesicles (IC50<0.2 {micro}M) and primary parasite cells (IC50<0.3 {micro}M), with active concentrations largely corresponding to NEN levels reachable in the liver. Metabolic analysis suggested that NEN acts as a mitochondrial uncoupler. Electron microscopy showed that NEN-treatments induced profound structural damage in the metacestode vesicle tissue, but mitochondrial ultrastructure was not notably affected. In mice intraperitoneally infected with E. multilocularis, NEN was orally administered during 9 weeks either alone, or in combination with albendazole. Pharmacokinetic analyses showed that NEN reached blood level concentrations above 1 {micro}M. However, the parasite burden in NEN-treated mice was not significantly reduced. Conclusions/SignificanceAlthough niclosamide and NEN demonstrated potent activity against E. multilocularis in vitro, this efficacy did not translate in the mouse model. The lack of in vivo activity could be attributed to several factors such as infection model, limited drug uptake by the parasite in the animal, or the rapid metabolization of the compound. Future studies should explore novel niclosamide derivatives and formulations to enhance efficacy against AE in vivo. Author SummaryAlveolar echinococcosis (AE) is a severe disease caused by the larval stage of the fox tapeworm Echinococcus multilocularis. The parasite forms tumor-like lesions in the liver and can spread to other organs. The currently licensed drugs for the treatment of AE are not always effective, require long-term use, and can cause side effects that frequently require treatment interruption. Therefore, safer and more efficacious treatment options are urgently needed. Niclosamide is frequently applied for the treatment of adult tapeworm infections in the intestine, but its limited uptake and low biodistribution renders the compound unsuitable for systemic treatment. In this study, we tested a non-toxic salt formulation, niclosamide ethanolamine (NEN), exhibiting improved absorption. In vitro, NEN was highly effective against E. multilocularis metacestode vesicles. It induced profound structural alterations in metacestode vesicles and impaired the mitochondrial membrane potential, and thus interfering in energy production. However, NEN was not effective against AE in experimentally infected mice. Our results suggest that NEN treatment appears promising in vitro, but to translate to the in vivo situation, new formulations and delivery strategies should be developed to increase absorption, bioavailability and metabolic stability of the compound for an effective treatment for AE.

pharmacology and toxicology↗

bioRxiv2025

Third-generation cephalosporin antibiotics induce phage bursts in the human gut microbiome.

The use of antibiotics disrupts the gut microbiota, potentially leading to long-term health issues and the spread of resistance. To investigate the impact of antibiotics on phage populations, we followed 22 healthy individuals two weeks before and up to six months after a three-day course of 3rd-generation cephalosporins. The populations of phages very rarely encoded antibiotic resistance genes and were mostly temperate including many phage-plasmids. Gut phages remained individual-specific even after microbiome perturbation by antibiotics. Yet, we found a 20% decline in phage diversity the day after treatment, alongside blooms of a few (mostly virulent) phages. We suggest that these temporary dominant phages contribute to the recovery of gut bacterial diversity through kill-the-winner dynamics. This is supported by the finding that several phages targeted Parabacteroides distasonis, a bacterium thriving after cephalosporin treatment, and which only proliferated when these phages were absent.Our findings suggest that phages play a crucial role in the gut microbiotas response to antibiotics by contributing to the restoration of microbial balance and diversity. HighlightsO_LIIn healthy individuals, cephalosporin antibiotics cause an approx. 20% decline in gut phage richness that is restored after 30 days C_LIO_LIHuman gut phage communities are specific of each individual, which is retained post-antibiotic treatment C_LIO_LIAntibiotic perturbation causes an increase in the number of dominant virulent phages supporting kill-the-winner dynamics as mechanisms for shaping bacterial diversity C_LIO_LIDominance of Parabacteroides distasonis (after cephalosporin treatment) is likely disrupted through its specific phages C_LI eTOCAntibiotic-induced disruption of the gut microbiome leads to a transient loss of microbiome diversity (bacterial and viral) and causes blooms of bacteria and their viruses. Our analysis suggests that these viruses prey on dominant bacteria, prevent their dominance, and contribute to the recovery of microbiome balance. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=96 SRC="FIGDIR/small/636470v2_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@98c366org.highwire.dtl.DTLVardef@1446921org.highwire.dtl.DTLVardef@51f941org.highwire.dtl.DTLVardef@1c328ed_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

Impact of the inoculum size on the in vivo activity of the aztreonam-avibactam combination in a murine model of peritonitis due to Escherichia coli expressing CTX-M-15 and NDM-1

BackgroundThe combination of aztreonam (ATM) and avibactam (AVI) is an attractive option to treat infections caused by extended spectrum {beta}-lactamase plus NDM-1-producing Enterobacteriaceae. Since ATM activity was shown to be severely impacted by an increase in the inoculum size in vitro, we wondered whether ATM-AVI activity could be impaired in high-inoculum infections. MethodsWe analyzed the impact of the inoculum size on ATM-AVI activity in vitro and in a murine model of peritonitis due to susceptible E. coli CFT073-pTOPO and its isogenic derivatives producing NDM-1 (E. coli CFT073-NDM1) and CTX-M-15 plus NDM-1 (E. coli CFT073-CTXM15-NDM1). The impact of the inoculum size on bacterial morphology was studied by microscopic examination. ResultsIn vitro, at standard (105) inoculum, E. coli CFT073-CTXM15-NDM1 was resistant to ATM but susceptible to the ATM-AVI combination. At high (107) inoculum, MICs of ATM alone and of the ATM-AVI combination reached > 512 and 64 mg/L respectively, against all tested strains. ATM led to bacterial filamentation when active against the bacteria, i.e., in monotherapy or in combination with AVI against susceptible E. coli CFT073-pTOPO, and only in combination with AVI against E. coli CFT073-CTXM15-NDM1. In vivo, increase in the inoculum led to a drastic decrease in the activity of ATM alone against E. coli CFT073-pTOPO, and of ATM-AVI against E. coli CFT073-CTXM15-NDM1. ConclusionOur results suggest a high in vivo impact of the inoculum increase on the activity of ATM alone against ATM-susceptible E. coli, and of ATM-AVI against CTX-M-15 plus NDM-1 producing E. coli. Clinicians must be aware of the risk of failures when using AZT-AVI in high inoculum infections.

microbiology↗

bioRxiv2022

High pathogenicity island, aer and sit operons: a "menage a trois" in Escherichia coli extra-intestinal virulence

The intrinsic virulence of extra-intestinal pathogenic Escherichia coli is attributed to numerous chromosome and/or plasmid-borne virulence associated genes (VAGs), encoding diverse functions as adhesins, toxins, protectins and iron capture systems, which occur in specific genetic backgrounds. Little is however known on their respective contribution to virulence. Here, by analyzing genomes of 232 sequence type complex (STc) 58 strains, we show that virulence quantified in a mouse model of sepsis emerged in a sub-group of STc58 due to the presence of the siderophore encoding high-pathogenicity island (HPI). When extending our analysis to 370 Escherichia strains we show that full virulence is associated with the presence of the aer or sit operons, in addition to the HPI. The prevalence of these operons, their co-occurrence and genomic location depend on the strain phylogeny. Selection of lineage-dependent specific associations of VAGs argues for strong epistatic interactions shaping the emergence of virulence in E. coli.

microbiology↗

bioRxiv2019

Success of Escherichia coli O25b:H4 ST131 clade C associated with a decrease in virulence

Escherichia coli of sequence type (ST) 131 resistant to fluoroquinolones and producer of CTX-M-15 is globally one of the major extraintestinal pathogenic E. coli (ExPEC). ST131 phylogenesis showed that multidrug-resistant ST131 strains belong to a clade called C, descending from an ancestral clade called B, comprising mostly antibiotic-susceptible strains. Antibiotic resistance could appear as one of the keys of the clade C global success. We hypothesized that other features of ST131 clade C could contribute to this success since other major global ExPEC clones (ST73, ST95) are mostly antibiotic-susceptible. To test this hypothesis, we measured the growth abilities, early biofilm formation and virulence-factor content of a collection of clade B and clade C strains. Moreover, using competition assays, we measured the capacity of selected representative strains of clades B and C to colonize the mouse intestine and urinary tract, and to kill mice in a septicemia model. Clade B and C strains had similar growth ability. However, clade B strains were more frequently early biofilm producers, expressed mostly faster their type 1 fimbriae and displayed more virulence factor-encoding genes than clade C strains. Clade B outcompeted clade C in the gut and/or urinary tract colonization models and in the septicemia model. These results strongly suggest that clade C strain evolution includes a loss of virulence, i.e. a process that could enhance micro-organism persistence in a given host and thus optimize transmission. This process, associated with acquired antibiotic-resistance, could ensure clade C strain survival in environments under antibiotic pressure.\n\nImportanceExtraintestinal pathogen Escherichia coli (ExPEC) are virulent but mostly antibiotic-susceptible. One worrying exception is ST131, a major multidrug resistant ExPEC clone that has spread worldwide since the 2000s. To contain the emergence of this threatening clone, we need to understand what factors favored its emergence and dissemination. Here, we investigated whether multidrug-resistant ST131 had advantageous phenotypic properties beyond multidrug resistance. To this end, we competed the emergent multidrug-resistant ST131 with its antibiotic-susceptible ancestor in different conditions: biofilm production, in vivo colonization and virulence experiments. In all in vivo competitions, we found that multidrug-resistant ST131 was losing to its ancestor, suggesting a lesser virulence of multidrug-resistant ST131. It was previously described that losing virulence can increase micro-organism persistence in some populations and subsequently its level of transmissibility. Thus, a decreased level of virulence, associated with multidrug resistance, could explain the global success of ST131.

microbiology↗

bioRxiv2019

Major role of the high-pathogenicity island (HPI) in the intrinsic extra-intestinal virulence of Escherichia coli revealed by a genome-wide association study

The genus Escherichia is composed of several species and cryptic clades, including E. coli, which behave as a vertebrate gut commensal, but also as an opportunistic pathogen involved in both diarrheic and extra-intestinal diseases. To characterize the genetic determinants of extra-intestinal virulence within the genus, we carried out an unbiased genome-wide association study (GWAS) on 370 commensal, pathogenic and environmental strains representative of the Escherichia genus phylogenetic diversity and including E. albertii (n=7), E. fergusonii (n=5), Escherichia clades (n=32) and E. coli (n=326), tested in a mouse model of sepsis. We found that the high-pathogenicity island (HPI), a [~]35 kbp gene island encoding the yersiniabactin siderophore, is highly associated with death in mice, surpassing other associated genetic factors also related to iron uptake, such as the aerobactin and the sitABCD operons. We validated the association in vivo by deleting key components of the HPI in E. coli strains in two phylogenetic backgrounds, and found that virulence is correlated in E. coli with growth in the presence of various stressors including several antimicrobials, which hints at collateral sensitivities associated with intrinsic virulence. This study points to the major role of iron capture systems in the extra-intestinal virulence of the genus Escherichia and the collateral effects on cell growth of such systems.

microbiology↗

bioRxiv2019

Genetic variation influences pluripotent ground state stability in mouse embryonic stem cells through a hierarchy of molecular phenotypes

Mouse embryonic stem cells (mESCs) cultured under controlled conditions occupy a stable ground state where pluripotency-associated transcriptional and epigenetic circuitry are highly active. However, mESCs from some genetic backgrounds exhibit metastability, where ground state pluripotency is lost in the absence of ERK1/2 and GSK3 inhibition. We dissected the genetic basis of metastability by profiling gene expression and chromatin accessibility in 185 genetically heterogeneous mESCs. We mapped thousands of loci affecting chromatin accessibility and/or transcript abundance, including eleven instances where distant QTL co-localized in clusters. For one cluster we identified Lifr transcript abundance as the causal intermediate regulating 122 distant genes enriched for roles in maintenance of pluripotency. Joint mediation analysis implicated a single enhancer variant ~10kb upstream of Lifr that alters chromatin accessibility and precipitates a cascade of molecular events affecting maintenance of pluripotency. We validated this hypothesis using reciprocal allele swaps, revealing mechanistic details underlying variability in ground state metastability in mESCs.

genomics↗